Mainly with GBA at the moment. All of my games are imported just fine but artwork isn't being downloaded. I'm guessing (just an assumption) it might have to do with the fact that GBA games have that wonky naming convention where they start with a number first.. like 0001, 0002, etc
I also noticed with some other games on other platforms that the box art will be MOSTLY correct but some games populate with .... well, stuff like this: